In Greek mythology the Erinyes or Eumenides (the Romans called them the Furies) were female personifications of vengeance. They were usually said to have been born from the blood of Uranus when Cronus castrated him. According to a variant account, they were born from Nyx. Their number is usually left indeterminate, though Virgil, probably working from an Alexandrian source, recognized three: Alecto ("unceasing"), Megaera ("grudging"), and Tisiphone ("avenging murder"). The heads of the Erinyes were wreathed with serpents, their eyes dripped with blood, and their whole appearance was terrific and appalling. Sometimes they had the wings of a bat or bird, or the body of a dog.

One myth had Tisiphone fall in love with Cithaeron. She caused his death by snakebite, specifically, one of the snakes from her head. Another myth says that the Erinyes struck the magical horse Xanthus dumb for rebuking Achilles.

The Erinyes generally stood for the rightness of things within the standard order; for example, Heraclitus declared that if Helios decided to change the course of the Sun through the sky, they would prevent him from doing so. But for the most part they were understood as the persecutors of mortal men and women who broke "natural" laws. In particular, those who broke ties of kinship through patricide, murdering a brother (Fratricide), or other such familial killings brought special attention from the Erinyes.

It was believed in early epochs that human beings might not have the right to punish such crimes, instead leaving the matter to the dead man's Erinyes to exact retribution. The goddess Nike filled a similar role. When not stalking victims on Earth, the Furies were thought to dwell in Tartarus, where they applied their tortures to the damned souls there.

The Erinyes are particularly known for the persecution of Orestes for the murder of his mother, Clytemnestra. Since Apollo had told Orestes to kill the murderer of his father, Agamemnon, and that person turned out to be his mother, Orestes prayed to him. Athena intervened and the Erinyes turned into the Eumenides ("goodly ones"), as they always did in their beneficial aspects.

Many scholars believe that they were originally referred to as the Eumenides not to reference their good sides but as a euphemism to avoid their wrath by calling them by their true name. This is similar to the taboo on speaking the names of certain spirits in many cultures. The Erinyes were also known as Semnai ("the venerable ones"), the Potniae ("the Awful Ones"), the Maniae ("the Madnesses") and the Praxidikae ("the Vengeful Ones").